strings: NewReader should have Seek, ReadAt

[rsc]

strings: NewReader should have Seek, ReadAt
but low priority; not for Go 1.

[rsc]

Comment 1:

Labels changed: added go1.1.

[edsrzf]

Comment 2:

These methods were added, but the CLs didn't mention this issue. See:
http://golang.org/cl/5639068
http://golang.org/cl/5675053

[robpike]

Comment 3:

Status changed to Fixed.